This invention relates to earth moving equipment and more particularly to excavating equipment utilizing a telescopically extendable boom with a digging bucket at the outermost end.
In the past there has been provided a piece of machinery for grading, excavating or other earth moving that has a boom capable of being extended and retracted. The boom can also be rotated as it is extended or retracted. The extending boom has attached to it a bucket at its outermost end which is used to excavate or otherwise move material. This equipment has been marketed under the name "Gradall" hydraulic excavators and is manufactured by The Gradall Company. The earth moving equipment is provided with hydraulic means connected to a mechanical linkage extending through the boom which is connected to and used to control the movement of the bucket. The hydraulic means to operate the linkage is located towards the base or cab end of the boom.
When using this type of equipment it was difficult, if not impossible, to unload materials from containers such as freight cars or trucks due to the angle of the bucket with respect to the boom and the container walls. In its normal configuration the boom could not be extended down into the container because of the limited pivotal movement of the boom and its inability to reach over and down into the container. The equipment was also limited in excavating applications whenever the excavation required removal of materials directly below the main body of the equipment as the boom could not be extended back under itself.
One solution was to provide an attachment onto the extendable boom which was at approximately 90.degree. with respect to the extendable boom. The existing mechanical linkage used to control the bucket was connected to additional mechanical linkage running through the 90.degree. attachment so that the operator could still control the bucket as it was lowered into the container or wherever the material was to be moved.
However, a problem with this arrangement was that the 90.degree. attachment that was added was set at one pre-determined angle and could not be varied. Furthermore, there was provided additional solid mechanical linkage to control the bucket through the 90.degree. attachment. Due to this solid linkage arrangement, the boom extension could only be set at one pre-determined angle which could not be varied. Another shortcoming of this arrangement was the additional weight of the linkage being added to the boom structure. Still another disadvantage was the limited added flexibility of the 90.degree.0 boom attachment. It could only be used in special applications such as extending over a freight car or truck container wall wherein a 90.degree. boom attachment may be acceptable. However, it could not be used in other applications where it may be desirable to have the attachment at only a small angle with respect to the main boom. Likewise, it would not function where it is necessary to have the boom and bucket extend back underneath the extendable boom for excavating in areas such as underneath bridges or viaducts while the piece of excavating machinery was positioned directly above the area to be excavated.
Another type of earth moving equipment is illustrated in U.S. Pat. No. 2,840,254 entitled "Clamshell Earth-Moving Machine." This patent shows a machine with a telescopic boom section having a hoe stick positioned at the outermost end of the boom. The hoe stick is pivotally mounted at approximately its center location and the upper end of the hoe stick is connected to a fluid actuated cylinder. The opposite end of the hoe stick has a clamshell bucket. There are at least two apparent shortcomings in this device. The first is the large size of the cylinder and piston required to pivot the hoe stick due to the design and mounting configuration. The second is that there is no means to provide for the hoe stick to be set and fixed at a predetermined angle. As the boom extends, and the cylinder and piston are held constant, the angle of the hoe stick with respect to the boom will change. This is an undesirable result as it requires the operator to go through several maneuvers to maintain the predetermined angle while extending the boom.
Other prior devices such as illustrated in U.S. Pat. Nos. 4,353,424; 3,445,015; 4,497,608; and 3,517,960 are not applicable to this invention as they do not address the problems of an earth moving machine having an extendable boom. Likewise, they do not provide for a pivotal joint on the end of an extendable telescopic boom such that a boom extension can be mounted at an angle with respect to the end of the extendable boom.
Applicant has solved the problems of the prior art by providing an earth moving machine having a first boom mounted on the base structure or platform of the machine. The first boom can be swiveled and pivoted on the base structure. There is a second boom telescopically received within the first boom. A third or extending boom is mounted to the outermost end of the second boom. In a first embodiment an adjustable joint connects one end of the third boom to the outermost end of the second boom at a pre-determined, fixed angle. By the use of additional linking members, the angle between the third and second booms can be adjusted. With this articulated connection, the third boom or boom extension can reach areas that were previously inaccessible by a conventional earth moving machine having a telescopic boom mounted relative to the first platform mounted boom. The bucket mounted at the end of the third or extension boom can reach areas directly underneath the earth moving machine in applications such as dredging streams beneath a bridge while the earth moving machine is parked directly above the area to be dredged. In order to provide the adjustable connecting joint, the hydraulic cylinder used to control the bucket movement is repositioned on the third or extending boom and connected to the power source by means of flexible hydraulic hoses. This eliminates the necessity of a solid linkage connecting the hydraulic cylinder to the bucket along the entire length of the booms.
In another embodiment the third boom or boom extension has one end connected to the outermost end of the telescopic boom by means of an adjustable joint having a hydraulic cylinder and piston mounted within the extending telescopically mounted boom. The adjustable ram or piston is connected to the third boom such that as the adjustable ram extends, the angle of the third boom relative to the extending boom can be dynamically adjusted.
Thus, it is an object of the present invention to provide an earth moving machine capable of having a first platform mounted boom which receives therein a telescopically mounted boom, and a third boom operably connected to the telescopically mounted boom such that one end of the third boom is mounted to the second boom by articulated connecting means so that the angle of the third boom with respect to the second boom can be varied.
Another object is to provide a third boom which is connected to the second extendable boom by means of an adjustable joint that can vary the angle between the second and third booms.
Related to this object is the object of providing a boom extension that can be connected at an acute angle with respect to the boom extension to allow the bucket to excavate in areas directly underneath the earth moving machine such as underneath a viaduct or bridge.
Yet another object is to provide a boom extension that can have the angle of the boom extension with respect to the extendable boom continuously varied by means of a hydraulic cylinder which controls the angle of the two booms with respect to each other.